Alloys



Patented Aug. 18, 1936 UNITED STATES PATIENT OFFlCE ALLOYS James M.Lohr, Morristown, N. J., assignor to Driver-Harris Company, Harrison, N.J., a corporation of New Jersey Application June 14, 1935,

No Drawing.

Serial No. 26,621

2 Claims,

of other known alloys, when used under high temperature conditions.

While nickel-chromium and nickel-chromiumiron alloys having the abilityto resist oxidation at high temperatures are known, their period ofusefulness in service is often not as long as desired. I have found thatthe addition of small quantities of zirconium to such nickel-chromiumalloys greatly increases their period of life when employed underconditions where they are subjected to high temperatures. The alloysforming the subject matter of the present application may also containsmall quantities of either silicon or manganese or both of theseelements.

In carrying out my invention I add small quantities of zirconium with orwithout silicon or manganese to nickel-chromium or nickelchromium-ironalloys. The nickel-chromium alloy most generally'used in the artconsists of 80 parts of nickel and parts of chromium and I find itadvantageous to add the other metals mentioned above to nickel-chromiumalloys of substantially these proportions. The proportions of nickel andchromium in the alloy may bevaried. Thus the chromium content may befrom 15 to percent and the balance nickel. 35 Likewise the mostgenerally used proportions of nickel, chromium and iron innickel-chromium-iron alloys is 60 percent nickel, 10 to 15 percentchromium and the balance iron and I find it advantageous to employsubstantially 40 these proportions of those ingredients, and add thezirconium. These proportions may also be varied, the nickel, however,forming the major part of the alloy, and the nickel-chromium contentbeingsuch that the alloy will have the char- 45 acteristics of anon-ferrous alloy.

In preparing alloys containing zirconium, the quantities of it aresubtracted from the nickel content, as for example, when zirconium isadded to an alloy containing "15 to 25 percent chromium 50 and thebalance nickel, the final alloy will contain 15 to 25 percent chromiumand zirconium in the percentages herein stated and the balance nickel.

The proportions of zirconium may vary within 55 certain limits. I havefound that best results are obtained when this metal is present in thenickelchromium or nickel-chromium+ir'0n alloy within the followinglimits: Percent Zirconium .01.50 5

If manganese or silicon are employed, they may be used within thefollowing limits:

' Percent Manganese 0.02-2.0 10 Silicon 0.02-2.0

The preferred proportions of the alloying agents are as follows:

Nickel-chromium and nickel-chromium-iron alloys containing zirconiumwithin the proporg0 tions given have been found by tests to have agreatly increased period of life when exposed to high temperatures. Forthe purpose of determining the life of such alloys at high temperaturesI have tested them by the method of test 25 outlined in TentativeAccelerated Life Tests for Metallic Materials for Electrical Heating ofthe American Society for Testing Materials described in vol. 29 of theProceedings of the Thirty- Second Annual Meeting of the American Society30 for Testing Materials" beginning on page 613. The method issubstantially as follows:

A sample of the wire to be tested, free from kinks, approximately,twelve inchesJong and of about .025" diameter, is mounted vertically onthe test board, the upper end being held in position by means of asuitable binding post. A 10 gram weight is attached to the lower/end ofthe specimen. A short piece of wire is attached to the 10 gram weightand projects downward into a cup of mercury where it may move freely upand down. A rheostat and an interrupter are connected in series with thespecimen to the power supply. The test is run on constant temperature ata standard temperature chosen for the alloy under consideration for thefirst twenty-four hours. Thereafter it is run on constant voltage to theburnout. The life in hours up to a 10 percent increase in resistance isknown as useful life while the life to the burnout is known as totallife. Throughout the test the power is on two minutes and off twominutes. This is accomplished by means of an interrupter.

In testing the alloys of my invention according to the above describedmethod a reference samchromium and no alloy addition having anapproximate lite of 90 hours was used. This value is considered as 100percent and the useful life of the samples tested is determined insponding percentage values. r

The addition of zirconium to such alloys within \the limits set forthabove increases the useful life to nearly- 200 percent where the wire isexposed to a hightemperature.

In the alloys referred to herein, small amounts correaosuoz ofphosphorus andsulphur may be present as impurities. The nickel may alsocontain about 1 percent of cobalt.

I claim:

2. An electric resistance element consisting I essentially of 15 to 25percent chromium, substantially JAMES M. LOHR.

.25 percent zirconium, balance nickel. 10

